1. Field of the Invention
The present invention relates to a lumber transfer system. More particularly, the present invention relates to a lumber transfer system for transferring pieces of lumber from a feeding conveyor to an outfeed conveyor.
2. Description of the Related Art
It is well known in the art that in a sawmill or a lumber mill, transportation of the lumbers requires the use of conveyors. Usually, the lumbers emerge from the mill in random order onto a feeding conveyor. Certain given stages of the transformation process require that the lumbers be regularly spaced apart on a conveyor. It is therefore necessary to provide a system for transferring the lumbers from the feeding conveyor to another conveyor such that the lumbers are regularly spaced thereon. In order to be efficient, lumber transfer systems should allow handling and transfer of any type, size and shape of lumbers such as stem, saw log, wood plank, beam and the like. Furthermore, they should also allow a high transfer rate of lumbers. In fact, the efficiency of a lumber mill generally depends greatly on the production rate attainable. The number of lumbers transferred per minute from one conveyor to another is thus an important factor affecting greatly the production rate of lumber mills.
Examples of transfer lumber systems known to the Applicant are described in the following Canadian patents and/or patent applications: 1,171,020; 1,228,873; 2,133,927; 2,148,322; 2,151,768; 2,185,609; 2,185,620; 2,238,231; 2,271,175; and 2,577,656.
It is also well known in the art that lumbers arriving on the feeding conveyor prior to being transferred and equally spaced by the transfer system are often intermingled and comprise different pieces of various lengths. Prior to being transferred, the lumbers are accumulated on an accumulating portion of the feeding conveyor, where typically, conveying chains roll at high speed. When a short lumber is followed by a long one, the long lumber has a tendency to pivot around the short lumber. Since the extremity of the longer lumber stands out relative to the downstream shorter lumber, this longer extremity is driven by the chains, and/or in some cases, by a pushing action of other following lumbers, and this situation leads to an important problem where the transfer system will load the long lumber together with the short one, while only the short lumber should have been transferred. When such problem occurs, production must be stopped and an operator must space out and put the lumbers back in order. Such a problem commonly occurs in lumber mills and affects the overall efficiency of the mills.
Hence, in light of the aforementioned, there is a need for an improved system which, by virtue of its design and components, would be able to overcome or at least minimize some of the aforementioned prior art problems.